Method and apparatus for cleaning metal objects



. Oct. 21, 1969 M. GRAF ETAI. 3,473,268

METHOD AND APPARATUS FOR CLEANING METAL OBJECTS Filed March 21. 1965 IN VENTORS rmx Gk 3,473,263 METHOD AND APPARATUS FOR CLEANING METAL OBJECTS Max Graf, Karlsruhe-Durlach, and Martin Weis, Ettlingen, near Karlsruhe, Germany, assignors to Badische Mascliinenfabrik G.m.b.I-I., Karlsruhe- Durlach, Germany Filed Mar. 21. 1966, Ser. No. 535,783 Claims priority, application Germany, Mar. 23, 1965,

rm. c1. B4c 3/08 US. Cl. 5113 11 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION For the purpose of cleaning castings and the like, various methods are known in which the workpieces are cleaned of molding sand, scale, and the like by blasting them with a blasting medium by employing a drumtype cleaning machine which is equipped with centrifugal wheels. In one of these known methods, the cleaning drum is rotatable about a horizontal axis and the mate rials to be cleaned are inserted into and discharged from this drum through openings in the outer wall of the drum which are adapted to be opened and closed by separate covers. In other known methods of this type, the workpieces are blasted within a cleaning drum which is rotatable about an obliquely inclined axis, and the materials to be cleaned are inserted into and discharged from the drum through separate openings, the inlet opening of which is located on the upper front side and the discharge opening within the lower part of the outer wall of the drum.

The known cleaning methods have a series of disadvantages. In drum-type cleaning machines which operate continuously, the workpieces are not uniformly blasted since, due to their different dimensions, they require different lengths of time to pass through the drum. Furthermore, there is the danger that some of the workpieces or broken parts thereof might become wedged between the revolving drum and the stationary wall of the housing which might result in interruptions of the operation of the machine or even in serious damage thereto. A continuous operation has the further disadvantage that the separation of different charges or the elimination of certain workpieces is very difiicult or may even be impossible.

The most important disadvantage of all known intermittent cleaning methods and the apparatus therefor is that the operations of loading and emptying the drum requires a considerable length of time since it is fir t necessary to stop the drum and then for reasons of safety to interrupt the supply of the blasting medium and the rotation of the centrifugal wheel before the drum can be opened. The frequent interruptions which are caused thereby considerably reduce the working capacity and efliciency of these apparatus.

States Patent O SUMMARY OF THE INVENTION It is an object of the present invention to provide an intermittently operative method of cleaning castings which, by means of a drum-type cleaning machine which is rotatable about an inclined axis, eliminates the abovementioned disadvantages of the known continuous and intermittent cleaning methods and is superior to these methods also by permitting a much higher output of cleaned workpieces to be attained within the actual cleaning time as compared with the length of time which is required for loading and emptying the drum.

For attaining this object, the invention provides that, when the blasting operation is completed, the continuously revolving cleaning drum is emptied of its contents through an opening in the lower end of the drum which is adapted to be closed by a discharge cover. One feature of the invention consists in providing this discharge cover in the form of a part of the bottom of the drum which is adapted to be pivoted away from the drum and, after the cleaned workpieces have been discharged from the drum, to be pivoted back against the drum so as to close the discharge opening. Another feature of the invention provides that, after the discharge opening has been closed, a new load of workpieces which are to be blasted within the drum is inserted into the latter through an inlet opening in the upper end of the drum which is adapted to be opened and closed by another cover. The operations of loading and emptying the drum may be carried out according to the invention during the continuous rotation of the centrifugal wheel. An important advantage of the inventive method over the previous methods is that it avoids the time-wasting operation of stopping the cleaning drum whenever a new load of workpieces is inserted and of then again starting the drum, and of also stopping and starting the centrifugal wheel. This results in a considerable reduction in the total length of time required for each load of workpieces to be cleaned and thus in a considerable saving of energy.

It is another preferred feature of the invention that, when the period required for the cleaning operation is completed, the part of the drum bottom which forms the discharge cover and is adapted to be pivoted for opening the drum, will be opened automatically already at a time when it is located in an angular position of 30 to 120 before reaching its lowest position, and that this cover will also be closed automatically when it is in an angular position of 30 to 120 after passing through its lowest position. The continuously revolving cleaning drum is therefore emptied of its contents while its discharge opening passes through an angle of about 60 to about 240 symmetrically to its lowest position during each revolution of the drum.

For loading the cleaning drum while it rotates continuously, a stationary supply bin is preferably mounted above the upper end of the drum and provided at its lower side with a pivotable loading cover for the cleaning drum which is adapted to open and close an inlet opening in a stationary plate which covers the upper end of the cleaning drum. The loading cover may be operated in the same manner as the discharge cover by a hydraulic or pneumatic cylinder which may be controlled automatically by time-controlled or other suitable means.

The means for automatically controlling the supply of blasting medium to the centrifugal wheel in accordance with the operative positions of the loading cover and discharge cover may be of any suitable conventional type. They should be designed so as to effect a supply of blasting medium to the centrifugal wheel when the loading cover as well as the discharge cover on the drum bottom are closed, and to interrupt the supply of blasting medium to the centrifugal wheel when the loading cover and/or the discharge cover are opened. The apparatus according to the invention may be further provided with suitable means for locking the loading cover and the discharge cover relative to each other so that whenever one of these covers is opened, the other cover will remain locked.

BRIEF DESCRIPTION OF THE DRAWING The features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying diagrammatic drawing which shows a side view, partly in vertical section, of the drumtype cleaning machine according to the invention.

DETAILED DESCRIPTION OF THE DRAWING This cleaning machine comprises a cleaning drum 1 which is mounted so as to be rotatable about an inclined axis extending at an angle of 15 to 45 to the horizontal and which is adapted to be driven at any desired speed by suitable driving means 18. Above the upper end of drum 1 and coaxially thereto a centrifugal wheel 2 is provided which is adapted to direct a current of cleaning material into the drum and upon the workpieces therein so as to clean the same. The upper opening 3 of drum 1 is covered by a stationary plate 4 which partly consists of a loading cover 6 which is pivotable about an axis and closes a supply bin 7 which is mounted in a stationary position above drum 1. The lower end or bottom of the drum consists of two parts 8 and 9 which are obliquely inclined to each other and project toward the outside of the drum. The bottom part 8 is rigidly secured to the wall of drum 1 and also to a housing 10 which extends underneath the drum and coaxially thereto and forms a support for the drum. The other bottom part 9 which forms a discharge cover is adapted to be held in its closed position by a onearmed lever 11 which is pivotably connected to the housing 10 by a bearing member 13 and adapted to be pivoted by a piston rod 12', the piston of which is slidable within a pneumatic or hydraulic cylinder 12. For connecting the lever 11 to the outer end of piston rod 12', a connecting link is pivotably mounted at one end on lever 11 by a pivot bearing 14 and connected at its other end to piston rod 12' by a bearing 14 so as to be freely rotatable about the axis of cylinder 12 and piston rod 12'.

Cylinder 12 is nonrotatable about its axis but pivotable in all directions by being connected to a universal joint 15 which is mounted in a fixed position. Housing 10 is mounted on and guided by an annular anti-friction bearing 16 and adapted to rotate together with drum 1, its bottom 8, 9, and lever 11 about the axis of drum 1.

The bottom 8, 9 of the drum is partly or entirely perforated at 19 so as to permit the blasting medium to escape from the drum and to drop through the bottom 8, 9 upon suitable conveying means 17 underneath the drum and then to be conveyed away by these means.

The mode of operation of the cleaning machine is as follows:

The workpieces to be cleaned are inserted into the continuously revolving drum 1 through the upper opening 3. After the loading cover 6 is closed, the supply of blasting medium to the centrifugal wheel 2 is started by actuator 20 opening blasting medium supply means valve 21 which also revolves while the drum is being charged. When the period required for the cleaning operation is terminated, the discharge cover 9 of the drum bottom is opened by the operation of the pneumatic or hydraulic cylinder 12, and the piston rod 12. At the same time or shortly before cover 9 is opened, the supply of the blasting medium to the centrifugal wheel 2 is interrupted by conventional control means 22 that controls operation of motor 23 that drives centrifugal Wheel 2. The opening movement of the drum bottom is likewise controlled by conventional means 24, comprising an abutment mounted on the drum 1 for rotation therewith and stationary switches, which move the piston rod 12' so as to permit the discharge cover 9 to open automatically when it is in an angular position of 30 to 120 before it reaches its lowest position. The blasted workpieces will then slide out of the drum and upon suitable conveying means 17 which are disposed underneath the discharge cover 9. When the discharge cover 9 is again in an angular position of 30 to after passing beyond its lowest position, it is closed by piston rod 12. Depending upon the kind of workpieces to be cleaned, it may sometimes be advisable to close the cover 9 at a later time or after the drum has carried out one complete revolution. Thereafter, the loading cover 6 on the supply bin 7 is opened and a new load of workpieces is fed into the drum. After the loading cover 6 has been closed, the supply of blasting medium to the centrifugal wheel 2 is again started.

The cleaning machine as previously described may be designed so as to be operated by hand, in which case the advantages are attained as are previously mentioned. For larger cleaning apparatus it is, however, also possible by the provision of relatively simple additional means o control the operation of the machine automatically so that some or all manual operations may be omitted. Thus, for example, suitable means 20, 21, 22 and 25 may be provided for preventing the supply of blasting medium from starting while the loading cover 6 and/or the discharge cover 9 is opened. Further safety measures which may be provided may consist of conventional means including 22, 25 for locking the loading cover 6 and the discharge cover 9 relative to each other in such a manner that the loading cover 6 can be opened only when the discharge cover 9 is closed and the latter can be opened only when the loading cover 6 is closed.

Although our invention has been illustrated and described with reference to the preferred embodiment thereof, we wish to have it understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed our invention, what we claim is:

1. An apparatus for cleaning objects by blasting them with a blasting medium comprising a cleaning drum mounted so as to be rotatable about an obliquely inclined axis, means for rotating said drum continuously, said drum having an inlet opening at its upper end and a drum bottom at its lower end, a stationary supply bin above said upper end of said drum, a pivotable loading cover for opening said supply bin toward said inlet opening so as to load said drum and for then closing said bin, at least a part of said drum bottom being pivotable toward the outside of said drum so as to open the same for emptying said drum, a centrifugal wheel adjacent to said inlet opening, and means for intermittently supplying a blasting medium to said centrifugal wheel for propelling said medium into said drum for cleaning each load of workpieces therein.

2. An apparatus as defined in claim 1, in which said drum bottom consists of two parts which are inclined at an angle to each other toward the outside of said drum, one of said parts being rigidly secured to the side wall of said drum, and the other part forming a discharge cover, a one-armed lever pivotably mounted at one end on said drum so as to be rotatable therewith, said discharge cover being mounted on the other end of said lever, 21 unit comprising a cylinder and a piston slidable within said cylinder and having a piston rod thereon connected to said lever for pivoting the same so as at least to close said discharge cover when said piston is acted upon a pressure medium.

3. An apparatus as defined in claim 2, further comprising a housing supporting said drum and rigidly secured to said bottom part which is rigidly connected to the side wall of said drum, an annular antifriction bearing for rotatably mounting and guiding said housing and said drum thereon, and a universal joint mounted in a fixed position, said cylinder being connected at its lower end to said universal joint so as to be nonrotatable but pivotable in all directions.

4. An apparatus as defined in claim 1, further comprising a stationary plate covering the upper end of said drum and having an inlet opening, said loading cover being adapted to open and close said inlet opening.

5. An apparatus as defined in claim 2, further comprising means for automatically controlling the supply of blasting medium to said centrifugal wheel in accordance with the operating positions of said loading and discharge covers and for eifecting the supply of blasting medium to said centrifugal wheel when said drum bottom is closed and for interrupting the sup-ply of blasting medium when at least said loading cover is opened.

6. An apparatus as defined in claim 2, further com prising means for locking said loading cover and said discharge cover relative to each other so that at any time only one of said covers can be opened.

7. An apparatus as defined in claim 3, in which said drum bottom is perforated, and further comprising conveying means underneath said drum for receiving and conveying away the used blasting medium and the cleaned workpieces.

8. A method for the accelerated charging and discharging of a blast cleaning machine having an inclined drum, an elevated inlet opening, a lower discharge opening and a fan blower for supplying the blasting medium to the drum, comprising the steps of: continuously rotating the drum during the complete method; continuously rotating the fan blower during the complete method; charging the drum with a batch of material to be treated; supplying blasting medium to the continuously rotating fan blower after the charging of the drum and after a predetermined time discontinuing the supply of the blasting medium to the fan blower; thereafter, discharging the treated material from the lower discharge opening of the continuously rotating drum.

9. The method according to claim 8, including the steps of closing the inlet opening after the charging of the drum and before the supplying of the blasting medium; closing the discharge opening prior to the subsequent supplying of blasting medium.

10. An apparatus for cleaning objects by blasting them with a blasting medium comprising: a cleaning drum mounted to be rotatable about an obliquely inclined axis; means for continuously rotating said drum; said drum having an inlet opening at its upper end and an outlet opening at its bottom end; means for selectively opening and closing said outlet opening during the continuous rotation of said drum.

11. The apparatus according to claim 10, including a continuously rotating means for propelling blasting medium into the drum; means for selectively supplying blasting medium to said last mentioned continuously rotating means only when said outlet opening is closed.

References (Iited UNITED STATES PATENTS 1,462,295 7/1923 Moore et al. 51-13 2,116,160 5/1938 Rosenberger et al 51-13 2,131,260 9/1938 Temple 51-164 3,103,766 9/1963 Freeman et a1. 5113 FOREIGN PATENTS 434,712 9/1935 Great Britain.

LESTER M. SWINGLE, Primary Examiner US. 01. X.R. 51 3 19 

